1. Field of the Invention
This invention relates to tamper indicating closures for application to container necks. The tamper indicating feature indicates that the closure has been previously removed or an attempt has been made to remove it from the container. More particularly, this invention relates to a tamper indicating closure in which a tamper indicating band depends from the bottom of the cap skirt by spaced frangible webs. The band has a stop which coacts with a stop on the container neck so that as the closure cap is being unthreaded from the container neck the tamper indicating band is restrained against axial or rotational movement causing fracture of the frangible webs and separation of the band from the cap.
2. Description of the Related Art
At the present time, one of the most commonly used stop means for restraining the movement of the tamper indicating band relative to the container neck and the cap has been the provision of an inwardly directed bead on the tamper indicating band which coacts with an outwardly directed flange on the container neck. In the process of threading the cap onto the container neck the bead on the tamper indicating band snaps over the flange on the container neck. In the unthreading process, the bead is restrained against axial motion by the container flange so that the frangible webs between the bottom of the cap skirt and the top of the tamper indicating band are fractured primarily in tension. There are many shortcomings with this type of tamper indicating band restraint. Among these are skewing of the band so that not all of the tamper indicating webs are broken during the unthreading process. This type of difficulty can be obviated by changing the stops to cooperating ratchet teeth on the tamper indicating band and container neck. In the unthreading direction, radial stop surfaces on the band ratchet teeth abut radial stop surfaces on the container neck ratchet teeth. The frangible webs are thus caused to fracture primarily in shear since the band does not rotate with the cap. However, much more turning torque must be applied to the cap to fracture the webs than with the more gradual stretching of the webs in the bead/flange combination where continued rotation moves the band and the bottom of the cap skirt axially apart as the band bead frictionally engages the container flange during this rotation. With both the cooperating bead/flange embodiment and the cooperating ratchet teeth embodiment there is a likelihood of fracturing the webs during the threading-on operation. In each case, the band must be stretched outwardly in a radial direction either to snap the band bead over the container flange or simultaneously snap the band ratchet teeth over the container neck ratchet teeth.